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package it.unimi.dsi.big.mg4j.index;
/*
* MG4J: Managing Gigabytes for Java (big)
*
* Copyright (C) 2007 Paolo Boldi and Sebastiano Vigna
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 3 of the License, or (at your option)
* any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, see singletonIntervalIterator;
/** The key index. */
private final Index keyIndex;
/** The cached copy of {@link #index index.pointerCoding}. */
protected final Coding pointerCoding;
/** The cached copy of {@link #index index.countCoding}. */
protected final Coding countCoding;
/** The cached copy of {@link #index index.positionCoding}. */
protected final Coding positionCoding;
/** The parameter b for Golomb coding of pointers. */
protected int b;
/**
* The parameter log2b for Golomb coding of pointers; it is the most
* significant bit of {@link #b}.
*/
protected int log2b;
/** The current term. */
protected long currentTerm = -1;
/** The current frequency. */
protected long frequency;
/**
* Whether the current terms has pointers at all (this happens when the {@link #frequency}
* is smaller than the number of documents).
*/
protected boolean hasPointers;
/** The current count (if this index contains counts). */
protected int count;
/**
* The last document pointer we read from current list, -1 if we just read the frequency,
* {@link DocumentIterator#END_OF_LIST} if we are beyond the end of list.
*/
protected long currentDocument;
/** The number of the document record we are going to read inside the current inverted list. */
protected long numberOfDocumentRecord;
/** This variable tracks the current state of the reader. */
protected int state;
/** Whether the index will use variable quanta. */
private boolean variableQuanta;
/** The parameter h (the maximum height of a skip tower). */
public final int height;
/** The quantum. */
public long quantum;
/** The bit mask giving the remainder of the division by {@link #quantum}. */
private long quantumModuloMask;
/** The shift giving result of the division by {@link #quantum}. */
private int quantumDivisionShift;
/**
* The maximum height of a skip tower in the current block. May be less than {@link #height}
* if the block is defective, and will be -1 on defective quanta (no tower at all).
*/
private int maxh;
/** The maximum valid index of the current skip tower, if any. */
private int s;
/**
* The minimum valid index of the current skip tower, or {@link Integer#MAX_VALUE}. If
* {@link #maxh} is negative, the value is undefined.
*/
private int lowest;
/** We have w = Hq. */
private long w;
/** The bit mask giving the remainder of the division by {@link #w}. */
private long wModuloMask;
/** The shift giving result of the division by {@link #w}. */
private int wDivisionShift;
/** The Golomb modulus for a top pointer skip, for each level. */
private int[] towerTopB;
/** The most significant bit of the Golomb modulus for a top point[]er skip, for each level. */
private int[] towerTopLog2B;
/** The Golomb modulus for a lower pointer skip, for each level. */
private int[] towerLowerB;
/** The most significant bit of the Golomb modulus for a lower pointer skip, for each level. */
private int[] towerLowerLog2B;
/** The prediction for a pointer skip, for each level. */
private long[] pointerPrediction;
/** An array to decode bit skips. */
private long[] bitSkip;
/** An array to decode positions bit skips. */
private long[] positionsBitSkip;
/** An array to decode the pointer skips. */
private long[] pointerSkip;
/** The number of bits read just after reading the last skip tower. */
private long readBitsAtLastSkipTower;
/** The document pointer corresponding to the last skip tower. */
private long pointerAtLastSkipTower;
/** The number of positions that should be skipped manually
* once the last read tower has been reached by skipping {@link #positionsToReadToReachCurrentPosition}.
*/
private long positionsToReadToReachCurrentPosition;
/** The offset in the positions stream from the start of the current quantum
* to the start of the last tower.
*/
private long positionsBitsOffset;
/** The last increment added to {@link #positionsBitSkip}. */
private long lastPositionsIncrement;
/** The current quantum bit length, as provided by the index. */
private int quantumBitLength;
/** The current positions quantum bit length, as provided by the index. */
private int positionsQuantumBitLength;
/** The current entry bit length, as provided by the index. */
private int entryBitLength;
/** This value of {@link #state} means that we are positioned just before a tower. */
private static final int BEFORE_TOWER = 0;
/**
* This value of {@link #state} can be assumed only in indices that contain counts; it means
* that we are positioned just before the count for the current document record.
*/
private static final int BEFORE_COUNT = 1;
/** This value of {@link #state} means that we are at the start of a new document record,
* unless we already read all documents (i.e., {@link #numberOfDocumentRecord} == {@link #frequency}),
* in which case we are at the end of the inverted list, and {@link #currentDocument} is {@link #END_OF_LIST}. */
private static final int BEFORE_POINTER = 2;
/** Whether the positions for the current document pointer have not been fetched yet. */
private boolean positionsUnread;
/** The cached position array. */
protected int[] positionCache = new int[ 16 ];
/** The offset of the positions of the {@linkplain #currentTerm current term}. */
protected long lastPositionsOffset;
public BitStreamHPIndexReaderIndexIterator( final BitStreamHPIndexReader parent, final InputBitStream ibs, final InputBitStream positions ) {
this.parent = parent;
this.ibs = ibs;
this.positions = positions;
index = parent.index;
keyIndex = index.keyIndex;
pointerCoding = index.pointerCoding;
countCoding = index.countCoding;
positionCoding = index.positionCoding;
intervalIterator = new IndexIntervalIterator();
singletonIntervalIterator = Reference2ReferenceMaps.singleton( keyIndex, (IntervalIterator)intervalIterator );
height = index.height;
if ( ! ( variableQuanta = index.quantum == 0 ) ) {
quantum = index.quantum;
quantumModuloMask = quantum - 1;
quantumDivisionShift = Fast.mostSignificantBit( quantum );
w = ( 1L << height ) * quantum;
wModuloMask = w - 1;
wDivisionShift = Fast.mostSignificantBit( w );
}
bitSkip = new long[ height + 1 ];
positionsBitSkip = new long[ height + 1 ];
pointerSkip = new long[ height + 1 ];
towerTopB = new int[ height + 1 ];
towerTopLog2B = new int[ height + 1 ];
towerLowerB = new int[ height + 1 ];
towerLowerLog2B = new int[ height + 1 ];
pointerPrediction = new long[ height + 1 ];
}
/** Debug variable, usually unused, that keeps track of the end of the positions stream for the current term (but not for term 0!). */
private long positionsLength;
/**
* Positions the index on the inverted list of a given term.
*
* This method can be called at any time. Note that it is always possible to
* call this method with argument 0, even if offsets have not been loaded.
*
* @param term a term.
*/
protected void position( final long term ) throws IOException {
if ( term == 0 ) {
if ( ASSERTS ) {
// Get end of positions
ibs.position( index.offsets.getLong( 1 ) );
positionsLength = ibs.readLongDelta();
}
ibs.position( 0 );
ibs.readBits( 0 );
lastPositionsOffset = ibs.readLongDelta(); // This is 0 for sure
positions.position( 0 );
}
else {
if ( index.offsets == null ) throw new IllegalStateException( "You cannot position an index without offsets" );
if ( ASSERTS ) {
// Get end of positions
if ( term < index.numberOfTerms - 1 ) {
ibs.position( index.offsets.getLong( term + 1 ) );
positionsLength = ibs.readLongDelta();
}
else positionsLength = Long.MAX_VALUE; // Presently, no way to check
}
ibs.position( index.offsets.getLong( term ) );
ibs.readBits( index.offsets.getLong( term ) );
// Let us position the positions bitstream
lastPositionsOffset = ibs.readLongDelta();
positions.position( lastPositionsOffset );
if ( ASSERTS ) if ( positionsLength != Long.MAX_VALUE ) positionsLength -= lastPositionsOffset;
if ( DEBUG ) if ( ASSERTS ) System.err.println( this + ": positions for term " + term + " start at bit " + lastPositionsOffset + " (" + positionsLength + " bits)" );
}
positions.readBits( 0 );
this.currentTerm = term;
readFrequency();
}
public long termNumber() {
return currentTerm;
}
protected IndexIterator advance() throws IOException {
if ( currentTerm == index.numberOfTerms - 1 ) return null;
if ( currentTerm != -1 ) {
skipTo( END_OF_LIST );
// This guarantees we have no garbage before the frequency
nextDocument();
positionsUnread = false;
}
// We must skip the offset into the positions bitstream
final long nextPositionsOffset = ibs.readLongDelta();
positions.skip( nextPositionsOffset - lastPositionsOffset - positions.readBits() );
lastPositionsOffset = nextPositionsOffset;
positions.readBits( 0 );
currentTerm++;
if ( ASSERTS ) positionsLength = -1; // Invalidate
readFrequency();
return this;
}
private void readFrequency() throws IOException {
// Read the frequency
switch ( index.frequencyCoding ) {
case GAMMA:
frequency = ibs.readLongGamma() + 1;
break;
case SHIFTED_GAMMA:
frequency = ibs.readLongShiftedGamma() + 1;
break;
case DELTA:
frequency = ibs.readLongDelta() + 1;
break;
default:
throw new IllegalStateException( "The required frequency coding (" + index.frequencyCoding + ") is not supported." );
}
if ( DEBUG ) System.err.println( this + ": Frequency for term " + currentTerm + " is " + frequency );
hasPointers = frequency < index.numberOfDocuments;
// We compute the modulus used for pointer Golomb coding
if ( pointerCoding == Coding.GOLOMB ) {
if ( hasPointers ) {
b = BitStreamIndex.golombModulus( frequency, index.numberOfDocuments );
log2b = Fast.mostSignificantBit( b );
}
}
if ( variableQuanta ) {
quantumDivisionShift = frequency > 1 ? ibs.readGamma() - 1 : -1;
if ( quantumDivisionShift == -1 ) quantumDivisionShift = Fast.ceilLog2( frequency ) + 1;
quantum = 1L << quantumDivisionShift;
quantumModuloMask = quantum - 1;
w = ( 1L << height ) * quantum;
wModuloMask = w - 1;
wDivisionShift = Fast.mostSignificantBit( w );
}
quantumBitLength = positionsQuantumBitLength = entryBitLength = -1;
lowest = Integer.MAX_VALUE;
if ( ASSERTS ) for ( int i = height; i > Math.min( height, Fast.mostSignificantBit( frequency >> quantumDivisionShift ) ); i-- )
pointerPrediction[ i ] = towerTopB[ i ] = towerLowerB[ i ] = -1;
final long pointerQuantumSigma = BitStreamIndex.quantumSigma( frequency, index.numberOfDocuments, quantum );
for ( int i = Math.min( height, Fast.mostSignificantBit( frequency >> quantumDivisionShift ) ); i >= 0; i-- ) {
towerTopB[ i ] = BitStreamIndex.gaussianGolombModulus( pointerQuantumSigma, i + 1 );
towerTopLog2B[ i ] = Fast.mostSignificantBit( towerTopB[ i ] );
towerLowerB[ i ] = BitStreamIndex.gaussianGolombModulus( pointerQuantumSigma, i );
towerLowerLog2B[ i ] = Fast.mostSignificantBit( towerLowerB[ i ] );
pointerPrediction[ i ] = ( quantum * ( 1L << i ) * index.numberOfDocuments + frequency / 2 ) / frequency;
}
count = -1;
currentDocument = -1;
numberOfDocumentRecord = -1;
positionsBitsOffset = 0;
positionsBitSkip[ 0 ] = 0; // To avoid spurious tower updates on the first tower
positionsToReadToReachCurrentPosition = 0;
lastPositionsIncrement = 0;
state = BEFORE_POINTER;
}
public Index index() {
return keyIndex;
}
public long frequency() {
return frequency;
}
private void ensureCurrentDocument() {
if ( ( currentDocument | 0x8000000000000000L ) == -1 ) throw new IllegalStateException( currentDocument == -1 ? "nextDocument() has never been called for term " + currentTerm : "This reader is positioned beyond the end of list of term " + currentTerm );
}
public long document() {
return currentDocument;
}
public Payload payload() throws IOException {
throw new UnsupportedOperationException( "This index (" + index + ") does not contain payloads" );
}
public int count() throws IOException {
if ( DEBUG ) System.err.println( this + ".count()" );
if ( count != -1 ) return count;
if ( ASSERTS ) ensureCurrentDocument();
if ( state == BEFORE_TOWER ) readTower();
if ( ASSERTS ) if ( state != BEFORE_COUNT ) throw new IllegalStateException();
state = BEFORE_POINTER;
switch ( countCoding ) {
case UNARY:
count = ibs.readUnary() + 1;
break;
case SHIFTED_GAMMA:
count = ibs.readShiftedGamma() + 1;
break;
case GAMMA:
count = ibs.readGamma() + 1;
break;
case DELTA:
count = ibs.readDelta() + 1;
break;
default:
throw new IllegalStateException( "The required count coding (" + countCoding + ") is not supported." );
}
return count;
}
protected void updatePositionCache() throws IOException {
if ( DEBUG ) System.err.println( this + ".updatePositionCache()" );
positionsUnread = false;
count(); // This will force reading the tower and updating positionsBitsOffset, if necessary
if ( positionsBitsOffset > positions.readBits() ) {
if ( DEBUG ) System.err.println( this + ": positionsBitsOffset=" + positionsBitsOffset + ", positions.readBits()=" + positions.readBits() + ", skipping by " + ( positionsBitsOffset - positions.readBits() ) );
positions.skip( positionsBitsOffset - positions.readBits() );
}
if ( ASSERTS ) assert positionsToReadToReachCurrentPosition >= 0 : positionsToReadToReachCurrentPosition + " < 0";
if ( positionsToReadToReachCurrentPosition > 0 ) {
if ( DEBUG ) System.err.println( this + ":Skipping sequentially " + positionsToReadToReachCurrentPosition + " positions..." );
// We skip, inside the current quantum, the positions we haven't read
switch ( positionCoding ) {
case SHIFTED_GAMMA:
if ( COOKIES ) {
positionsToReadToReachCurrentPosition--;
if ( positions.readShiftedGamma() != Integer.MAX_VALUE ) throw new AssertionError();
}
positions.skipShiftedGammas( positionsToReadToReachCurrentPosition );
break;
case GAMMA:
if ( COOKIES ) {
positionsToReadToReachCurrentPosition--;
if ( positions.readGamma() != Integer.MAX_VALUE ) throw new AssertionError();
}
positions.skipGammas( positionsToReadToReachCurrentPosition );
break;
case DELTA:
if ( COOKIES ) {
positionsToReadToReachCurrentPosition--;
if ( positions.readDelta() != Integer.MAX_VALUE ) throw new AssertionError();
}
positions.skipDeltas( positionsToReadToReachCurrentPosition );
break;
default:
throw new IllegalStateException( "The required position coding (" + positionCoding + ") is not supported." );
}
}
// We must fix it so that nextDocument() will restore it to 0
positionsToReadToReachCurrentPosition = -count;
if ( COOKIES ) positionsToReadToReachCurrentPosition--;
if ( count > positionCache.length ) positionCache = new int[ Math.max( positionCache.length * 2, count ) ];
final int[] occ = positionCache;
switch ( positionCoding ) {
case SHIFTED_GAMMA:
if ( COOKIES ) if ( positions.readShiftedGamma() != Integer.MAX_VALUE ) throw new AssertionError();
positions.readShiftedGammas( occ, count );
for ( int i = 1; i < count; i++ ) occ[ i ] += occ[ i - 1 ] + 1;
return;
case GAMMA:
if ( COOKIES ) if ( positions.readGamma() != Integer.MAX_VALUE ) throw new AssertionError();
positions.readGammas( occ, count );
for ( int i = 1; i < count; i++ ) occ[ i ] += occ[ i - 1 ] + 1;
return;
case DELTA:
if ( COOKIES ) if ( positions.readDelta() != Integer.MAX_VALUE ) throw new AssertionError();
positions.readDeltas( occ, count );
for ( int i = 1; i < count; i++ ) occ[ i ] += occ[ i - 1 ] + 1;
return;
default:
throw new IllegalStateException( "The required position coding (" + index.positionCoding + ") is not supported." );
}
}
public IntIterator positions() throws IOException {
if ( ASSERTS ) ensureCurrentDocument();
if ( positionsUnread ) updatePositionCache();
return IntIterators.wrap( positionCache, 0, count );
}
public int[] positionArray() throws IOException {
if ( ASSERTS ) ensureCurrentDocument();
if ( positionsUnread ) updatePositionCache();
return positionCache;
}
// TODO: check who's using this (positionArray() is actually faster now)
public int positions( final int[] position ) throws IOException {
if ( ASSERTS ) ensureCurrentDocument();
if ( positionsUnread ) updatePositionCache(); // And also that positions have
// been read
if ( position.length < count ) return -count;
for ( int i = count; i-- != 0; )
position[ i ] = this.positionCache[ i ];
return count;
}
public long nextDocument() throws IOException {
if ( DEBUG ) System.err.println( "{" + this + "} nextDocument()" );
if ( state != BEFORE_POINTER ) {
if ( state == BEFORE_TOWER ) readTower();
if ( state == BEFORE_COUNT ) {
switch ( countCoding ) {
case UNARY:
count = ibs.readUnary() + 1;
break;
case SHIFTED_GAMMA:
count = ibs.readShiftedGamma() + 1;
break;
case GAMMA:
count = ibs.readGamma() + 1;
break;
case DELTA:
count = ibs.readDelta() + 1;
break;
default:
throw new IllegalStateException( "The required count coding (" + countCoding + ") is not supported." );
}
state = BEFORE_POINTER;
}
}
if ( currentDocument == END_OF_LIST ) return -1;
if ( ++numberOfDocumentRecord == frequency ) {
currentDocument = END_OF_LIST;
return -1;
}
if ( hasPointers ) {// We do not write pointers for everywhere occurring terms.
switch ( pointerCoding ) {
case UNARY:
currentDocument += ibs.readLongUnary() + 1;
break;
case SHIFTED_GAMMA:
currentDocument += ibs.readLongShiftedGamma() + 1;
break;
case GAMMA:
currentDocument += ibs.readLongGamma() + 1;
break;
case DELTA:
currentDocument += ibs.readLongDelta() + 1;
break;
case GOLOMB:
currentDocument += ibs.readLongGolomb( b, log2b ) + 1;
break;
default:
throw new IllegalStateException( "The required pointer coding (" + pointerCoding + ") is not supported." );
}
}
else currentDocument++;
if ( ASSERTS ) if ( numberOfDocumentRecord > quantum ) assert positionsBitsOffset > 0;
if ( ( numberOfDocumentRecord & quantumModuloMask ) == 0 ) {
state = BEFORE_TOWER;
positionsToReadToReachCurrentPosition = 0;
}
else {
state = BEFORE_COUNT;
if ( ASSERTS ) assert count > 0 : count + " <= " + 0;
positionsToReadToReachCurrentPosition += count;
if ( COOKIES ) positionsToReadToReachCurrentPosition++;
}
count = -1;
positionsUnread = true;
return currentDocument;
}
/**
* Reads the entire skip tower for the current position. This method assumes that the tower
* has been passed over sequentially, and correpondingly sets {@link #lastPositionsIncrement}
* to the number of positions bits of the last quantum.
*/
private void readTower() throws IOException {
lastPositionsIncrement = maxh >= 0 ? positionsBitSkip[ 0 ] : 0;
if ( DEBUG ) System.err.println( this + ": Setting lastPositionsIncrement to " + lastPositionsIncrement + " in readTower()" );
readTower( -1 );
if ( DEBUG ) System.err.println( this + ": Incrementing positionsBitsOffset by " + lastPositionsIncrement + " in readTower()" );
// TODO: this should be moved into readTower(int)
positionsBitsOffset += lastPositionsIncrement;
}
/**
* Reads the skip tower for the current position, possibly skipping part of the tower.
*
*
Note that this method will update {@link #state} only if it reads the entire tower,
* otherwise the state remains {@link #BEFORE_TOWER}.
*
* @param pointer the tower will be read up to the first entry smaller than or equal to this
* pointer; use -1 to guarantee that the entire tower will be read.
*/
private void readTower( final long pointer ) throws IOException {
int i, j, towerLength = 0;
long cacheOffset, cache, k;
long bitsAtTowerStart = 0;
boolean truncated = false;
if ( ASSERTS ) assert numberOfDocumentRecord % quantum == 0;
if ( ASSERTS ) if ( state != BEFORE_TOWER ) throw new IllegalStateException( "readTower() called in state " + state );
cacheOffset = numberOfDocumentRecord & wModuloMask;
k = cacheOffset >> quantumDivisionShift;
if ( ASSERTS ) if ( k == 0 ) { // Invalidate current tower data
it.unimi.dsi.fastutil.longs.LongArrays.fill( pointerSkip, Long.MAX_VALUE );
it.unimi.dsi.fastutil.longs.LongArrays.fill( bitSkip, Long.MAX_VALUE );
it.unimi.dsi.fastutil.longs.LongArrays.fill( positionsBitSkip, Long.MAX_VALUE );
}
// Compute the height of the current skip tower.
s = ( k == 0 ) ? height : Fast.leastSignificantBit( k );
cache = frequency - w * ( numberOfDocumentRecord >> wDivisionShift );
if ( cache < w ) {
maxh = Fast.mostSignificantBit( ( cache >> quantumDivisionShift ) - k );
if ( maxh < s ) {
s = maxh;
truncated = true;
}
else truncated = false;
}
else {
cache = w;
maxh = height;
truncated = k == 0;
}
// assert w == cache || k == 0 || lastMaxh == Fast.mostSignificantBit( k ^ (
// cache/quantum ) ) : lastMaxh +","+ (Fast.mostSignificantBit( k ^ ( cache/quantum )
// ));
i = s;
if ( s >= 0 ) {
if ( k == 0 ) {
if ( quantumBitLength < 0 ) {
quantumBitLength = ibs.readDelta();
positionsQuantumBitLength = ibs.readDelta();
entryBitLength = ibs.readDelta();
}
else {
quantumBitLength += Fast.nat2int( ibs.readDelta() );
positionsQuantumBitLength += Fast.nat2int( ibs.readDelta() );
entryBitLength += Fast.nat2int( ibs.readDelta() );
}
if ( DEBUG ) System.err.println( "{" + this + "} quantum bit length=" + quantumBitLength + " positions quantum bit length=" + positionsQuantumBitLength + " entry bit length=" + entryBitLength );
}
if ( DEBUG ) System.err.println( "{" + this + "} Reading tower; pointer=" + pointer + " maxh=" + maxh + " s=" + s );
if ( s > 0 ) {
towerLength = entryBitLength * ( s + 1 ) + Fast.nat2int( ibs.readDelta() );
if ( DEBUG ) System.err.println( "{" + this + "} Tower length=" + towerLength );
}
// We store the number of bits read at the start of the tower (just after the
// length).
bitsAtTowerStart = ibs.readBits();
if ( truncated ) {
if ( DEBUG ) System.err.println( "{" + this + "} Truncated--reading tops" );
// We read the tower top.
pointerSkip[ s ] = Fast.nat2int( ibs.readGolomb( towerTopB[ s ], towerTopLog2B[ s ] ) ) + pointerPrediction[ s ];
bitSkip[ s ] = quantumBitLength * ( 1L << s ) + entryBitLength * ( ( 1L << s + 1 ) - s - 2 ) + Fast.nat2int( ibs.readLongDelta() );
positionsBitSkip[ s ] = positionsQuantumBitLength * ( 1L << s ) + Fast.nat2int( ibs.readLongDelta() );
}
else {
// We copy the tower top from the lowest inherited entry suitably updated.
pointerSkip[ s ] = pointerSkip[ s + 1 ] - ( currentDocument - pointerAtLastSkipTower );
bitSkip[ s ] = bitSkip[ s + 1 ] - ( bitsAtTowerStart - readBitsAtLastSkipTower ) - towerLength;
// TODO: note that we could use the same method for pointers and bit skips!
positionsBitSkip[ s ] = positionsBitSkip[ s + 1 ] - positionsBitSkip[ s ];
if ( ASSERTS ) assert positionsBitSkip[ s ] > 0 : positionsBitSkip[ s ] + " <= " + 0;
}
// We read the remaining part of the tower, at least until we point after pointer.
if ( currentDocument + pointerSkip[ i ] > pointer ) {
for ( i = s - 1; i >= 0; i-- ) {
pointerSkip[ i ] = Fast.nat2int( ibs.readGolomb( towerLowerB[ i ], towerLowerLog2B[ i ] ) ) + pointerSkip[ i + 1 ] / 2;
bitSkip[ i ] = ( bitSkip[ i + 1 ] - entryBitLength * ( i + 1 ) ) / 2 - Fast.nat2int( ibs.readLongDelta() );
positionsBitSkip[ i ] = positionsBitSkip[ i + 1 ] / 2 - Fast.nat2int( ibs.readLongDelta() );
if ( DEBUG ) if ( currentDocument + pointerSkip[ i ] <= pointer ) System.err.println( "{" + this + "} stopping reading at i=" + i + " as currentDocument (" + currentDocument
+ ") plus pointer skip (" + pointerSkip[ i ] + ") is smaller than or equal target (" + pointer + ")" );
if ( currentDocument + pointerSkip[ i ] <= pointer ) break;
}
}
}
/*
* If we did not read the entire tower, we need to fix the skips we read (as they are
* offsets from the *end* of the tower) and moreover we must make unusable the rest of
* the tower (for asserts).
*/
if ( i > 0 ) {
final long fix = ibs.readBits() - bitsAtTowerStart;
for ( j = s; j >= i; j-- )
bitSkip[ j ] += towerLength - fix;
if ( ASSERTS ) for ( ; j >= 0; j-- )
pointerSkip[ j ] = Long.MAX_VALUE;
}
else state = BEFORE_COUNT;
// We update the inherited tower.
final long deltaBits = ibs.readBits() - readBitsAtLastSkipTower;
final long deltaPointers = currentDocument - pointerAtLastSkipTower;
if ( ASSERTS ) assert lastPositionsIncrement >= 0 : lastPositionsIncrement + " < " + 0;
for ( j = Fast.mostSignificantBit( k ^ ( cache >> quantumDivisionShift ) ); j >= s + 1; j-- ) {
bitSkip[ j ] -= deltaBits;
positionsBitSkip[ j ] -= lastPositionsIncrement;
pointerSkip[ j ] -= deltaPointers;
}
readBitsAtLastSkipTower = ibs.readBits();
pointerAtLastSkipTower = currentDocument;
lowest = i < 0 ? 0 : i;
if ( DEBUG ) {
System.err.println( "{" + this + "} " + "Computed skip tower (lowest: " + lowest + ") for document record number " + numberOfDocumentRecord + " (pointer " + currentDocument + ") from " + Math.max( i, 0 ) + ": " );
System.err.print( "% " );
for ( j = 0; j <= s; j++ )
System.err.print( pointerSkip[ j ] + ":" + bitSkip[ j ] + ":" + positionsBitSkip[ j ] + " " );
System.err.print( " [" );
for ( ; j <= height; j++ )
System.err.print( pointerSkip[ j ] + ":" + bitSkip[ j ] + ":" + positionsBitSkip[ j ] + " " );
System.err.print( "]" );
System.err.println();
}
if ( ASSERTS ) {
for ( j = Fast.mostSignificantBit( k ^ ( cache >> quantumDivisionShift ) ); j >= s + 1; j-- ) {
assert positionsBitSkip[ j ] >= 0 : "positionsBitSkip[" + j + "] = " + positionsBitSkip[ j ] + " < " + 0;
assert positionsBitSkip[ j ] >= positionsBitSkip[ j - 1 ] :
"positionsBitSkip[" + j + "] = " + positionsBitSkip[ j ] + " < " + positionsBitSkip[ j - 1 ] + " = positionsBitSkip[" + ( j - 1 ) + "]";
}
}
}
public long skipTo( final long p ) throws IOException {
if ( DEBUG ) System.err.println( this + ".skipTo(" + p + ") [currentDocument=" + currentDocument + ", numberOfDocumentRecord=" + numberOfDocumentRecord + ", positionsBitsOffset=" + positionsBitsOffset + "]" );
// If we are just at the start of a list, let us read the first pointer.
if ( numberOfDocumentRecord == -1 ) nextDocument(); // TODO: shouldn't we just read the
// tower?
if ( currentDocument >= p ) {
if ( DEBUG ) System.err.println( this + ": No skip necessary, returning " + currentDocument );
return currentDocument;
}
if ( state == BEFORE_TOWER ) {
lastPositionsIncrement = maxh >= 0 ? positionsBitSkip[ 0 ] : 0;
readTower( p );
if ( DEBUG ) System.err.println( this + ": Incrementing positionsBitsOffset by " + lastPositionsIncrement + " in skipTo() initial phase" );
positionsBitsOffset += lastPositionsIncrement;
}
final long[] pointerSkip = this.pointerSkip;
for ( ;; ) {
if ( ASSERTS ) assert maxh < 0 || lowest > 0 || pointerSkip[ 0 ] != Long.MAX_VALUE;
// If on a defective quantum (no tower) or p is inside the current quantum (no
// need to scan the tower) we bail out.
if ( maxh < 0 || lowest == 0 && pointerAtLastSkipTower + pointerSkip[ 0 ] > p ) break;
if ( DEBUG ) System.err.println( this + ": In for loop, currentDocument=" + currentDocument + ", maxh=" + maxh + ", numberOfDocumentRecord=" + numberOfDocumentRecord + ", p=" + p );
final long cacheOffset = numberOfDocumentRecord & wModuloMask;
final long k = cacheOffset >> quantumDivisionShift;
final int top = Fast.mostSignificantBit( k ^ ( Math.min( w, frequency - numberOfDocumentRecord + cacheOffset ) >> quantumDivisionShift ) );
int i;
for ( i = lowest; i <= top; i++ ) {
if ( ASSERTS ) if ( ( k & 1L << i ) != 0 ) assert pointerSkip[ i ] == pointerSkip[ i + 1 ];
if ( ASSERTS ) assert pointerSkip[ i ] != Long.MAX_VALUE : "Invalid pointer skip " + i + " (lowest=" + lowest + ", top=" + top + ")";
if ( pointerAtLastSkipTower + pointerSkip[ i ] > p ) break;
}
if ( --i < 0 ) break;
if ( ASSERTS ) assert i >= lowest : i + " < " + lowest;
if ( DEBUG ) System.err.println( this + ": Safely after for with i=" + i + ", P[i]=" + pointerSkip[ i ] + ", A[i]=" + bitSkip[ i ] + ", B[i]=" + positionsBitSkip[ i ] );
if ( DEBUG ) System.err.println( this + ": [" + ibs.readBits() + "] Skipping " + ( bitSkip[ i ] - ( ibs.readBits() - readBitsAtLastSkipTower ) ) + " bits ("
+ ( ( ( k & -( 1L << i ) ) + ( 1L << i ) ) * quantum - cacheOffset ) + " records) to get to document pointer " + ( currentDocument + pointerSkip[ i ] ) );
ibs.skip( bitSkip[ i ] - ( ibs.readBits() - readBitsAtLastSkipTower ) );
/* We accumulate the number of bits that must be skipped in the positions stream to reach the position
* corresponding to the current tower. */
if ( DEBUG ) System.err.println( this + ": Incrementing positionsBitsOffset by " + positionsBitSkip[ i ] + " (height " + i + ")" );
lastPositionsIncrement = positionsBitSkip[ i ];
positionsBitsOffset += lastPositionsIncrement;
if ( ASSERTS ) if ( positionsLength != -1 ) assert positionsBitsOffset <= positionsLength : positionsBitsOffset + " > " + positionsLength;
state = BEFORE_TOWER;
currentDocument = pointerSkip[ i ] + pointerAtLastSkipTower;
numberOfDocumentRecord += ( ( k & -( 1L << i ) ) + ( 1L << i ) ) * quantum - cacheOffset;
// If we skipped beyond the end of the list, we invalidate the current document.
if ( numberOfDocumentRecord == frequency ) {
currentDocument = END_OF_LIST;
positionsUnread = false;
state = BEFORE_POINTER; // We are actually before a frequency, but we must
// avoid that calls to nextDocument() read anything
}
else {
positionsUnread = true;
readTower( p ); // Note that if we are exactly on the destination pointer, we will read the entire tower.
}
count = -1; // We must invalidate count as readDocumentPointer() would do.
positionsToReadToReachCurrentPosition = 0;
if ( numberOfDocumentRecord >= frequency - 1 ) break;
}
if ( DEBUG ) System.err.println( this + ": Completing sequentially, currentDocument=" + currentDocument + ", numberOfDocumentRecord=" + numberOfDocumentRecord + ", p=" + p );
while ( currentDocument < p ) nextDocument();
if ( DEBUG ) System.err.println( this + ".toSkip(): Returning " + currentDocument );
return currentDocument;
}
public void dispose() throws IOException {
parent.close();
}
public boolean mayHaveNext() {
return numberOfDocumentRecord < frequency - 1;
}
public String toString() {
return index + " [" + currentTerm + "]" + ( weight != 1 ? "{" + weight + "}" : "" );
}
/**
* An interval iterator returning the positions of the current document as singleton
* intervals.
*/
private final class IndexIntervalIterator extends AbstractObjectIterator implements IntervalIterator {
int pos = -1;
public void reset() throws IOException {
pos = -1;
if ( positionsUnread ) updatePositionCache(); // This guarantees the position cache is ok
}
public void intervalTerms( final LongSet terms ) {
terms.add( BitStreamHPIndexReaderIndexIterator.this.currentTerm );
}
public boolean hasNext() {
return pos < count - 1;
}
public Interval next() {
if ( !hasNext() ) throw new NoSuchElementException();
return Interval.valueOf( positionCache[ ++pos ] );
}
public Interval nextInterval() {
return pos < count - 1 ? Interval.valueOf( positionCache[ ++pos ] ) : null;
}
public int extent() {
return 1;
}
public String toString() {
return index + ": " + currentTerm + "[doc=" + currentDocument + ", count=" + count + ", pos=" + pos + "]";
}
};
public Reference2ReferenceMap intervalIterators() throws IOException {
intervalIterator();
return singletonIntervalIterator;
}
public IntervalIterator intervalIterator() throws IOException {
return intervalIterator( keyIndex );
}
public IntervalIterator intervalIterator( final Index index ) throws IOException {
if ( ASSERTS ) ensureCurrentDocument();
// TODO: this was if ( index != keyIndex || hasPayloads )
if ( index != keyIndex ) return IntervalIterators.FALSE;
if ( ASSERTS ) assert intervalIterator != null;
intervalIterator.reset();
return intervalIterator;
}
public ReferenceSet indices() {
return index.singletonSet;
}
}
private IndexIterator documents( final CharSequence term, final long termNumber ) throws IOException {
indexIterator.term( term );
indexIterator.position( termNumber );
return indexIterator;
}
public IndexIterator documents( final long term ) throws IOException {
return documents( null, term );
}
public IndexIterator documents( final CharSequence term ) throws IOException {
if ( closed ) throw new IllegalStateException( "This " + getClass().getSimpleName() + " has been closed" );
if ( index.termMap != null ) {
final long termIndex = index.termMap.getLong( term );
if ( termIndex == -1 ) return index.getEmptyIndexIterator( term, termIndex );
return documents( term, termIndex );
}
throw new UnsupportedOperationException( "Index " + index + " has no term map" );
}
@Override
public IndexIterator nextIterator() throws IOException {
return indexIterator.advance();
}
public String toString() {
return getClass().getSimpleName() + "[" + index + "]";
}
public void close() throws IOException {
super.close();
indexIterator.ibs.close();
indexIterator.positions.close();
}
}